What is 86 extension?

As an AI language model, I am unable to determine the exact context and specific meaning of "86 extension." However, "86" is a slang term that means "to get rid of" or "to discard," and an "extension" generally refers to the addition or lengthening of something. Therefore, "86 extension" could possibly refer to a discarded or removed extension of something. It is important to note that this is just a guess and additional context is needed to provide a more accurate answer.